1. Field of the Invention
The present invention relates generally to managing signal interference on a printed circuit board and, more particularly, to interference signal decoupling using a board-level EMI shield that adheres to and conforms with printed circuit board component and board surfaces.
2. Related Art
As large scale integrated circuits operate at increasingly higher speeds, the need for devices to operate at faster switching rates has increased. As switching rates increase, problems which do not exist at lower speeds, such as shielding electronics from external sources of electromagnetic interference (EMI), become increasingly problematic. Moreover, maintaining sufficient electrical noise isolation and limiting inductance between components becomes more difficult as the frequency at which a circuit operates increases.
Conventionally, a shielded enclosure in the form of a metallic box or cage is placed around printed circuit board components to prevent unwanted electromagnetic energy from impinging on the protected components. Such metallic enclosures have numerous drawbacks that limit their shielding effectiveness. For example, electromagnetic energy often penetrates the on-board metallic enclosure at gaps between the cage and the printed circuit board surface. As a result, external electromagnetic fields can be capacitvely (electrostatically) coupled onto traces on the printed circuit board, magnetically coupled to conductive loops on the printed circuit board, or electromagnetically coupled to conductors acting as small antennas of electromagnetic radiation. In addition, power and signal lines are typically connected to interconnect posts mounted on the printed circuit board to receive power and transfer communication signals. Interfering signals conducted along such power and signal lines can enter the metallic enclosure.